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Re: [tor-bugs] #3460 [Tor Hidden Services]: Replay-detection window for HS INTRODUCE2 cells causes HS reachability failures (was: Expand replay-detection window for HS INTRODUCE2 cells)
#3460: Replay-detection window for HS INTRODUCE2 cells causes HS reachability
failures
---------------------------------+------------------------------------------
Reporter: rransom | Owner: rransom
Type: task | Status: new
Priority: normal | Milestone: Tor: 0.2.2.x-final
Component: Tor Hidden Services | Version:
Keywords: | Parent:
Points: | Actualpoints:
---------------------------------+------------------------------------------
Changes (by rransom):
* milestone: Tor: 0.2.3.x-final => Tor: 0.2.2.x-final
Comment:
My plan for how to fix this no longer involves expanding the replay-
detection window, even on 0.2.2.x.
The Right Thing is to split our current 60-minute per-hidden-service (at
least I hope it's per-HS) replay-detection cache (which handles both
clients' DH public keys and the RSA-encrypted portions of INTRODUCE2
cells) into a per-HS DH public key replay cache that only holds entries
for five minutes, purely as a performance improvement (so we continue to
not launch multiple attempts to connect to a single rendezvous point), and
a per-intro-point replay cache that holds the non-malleable part of the
INTRODUCE2 message for the lifetime of the intro point, to provide
security against replay attacks.
The easiest way to limit the size of the per-intro-point replay cache will
be to limit the number of INTRODUCE2 cells sent to each intro point before
it is replaced.
I'm setting this ticket back to 0.2.2.x, because the scary part of this
change will be making intro points expire after a while, and we need to
apply that to 0.2.2.x in order to fix the service-side part of #3825.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3460#comment:2>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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